微粒體甲烷單氧化酵素之模型 三核銅金屬簇化物之研究

Models of the Particulate Methane Monooxygenase(pMMO): Trinuclear Copper Clusters

蘇柏瑋

指導教授 ： 陳炳宇 ； 李位仁

國立臺灣師範大學/理學院/化學系/碩士(2012年)

摘要

在本篇研究中，我們合成出全新的含氮配位基7-ImPy以及7-MeImPy，能與一價銅離子[CuI(CH3CN)4](BF4)配位形成三核銅簇離子化合物[CuICuICuI(7-ImPy)](BF4) 和 [CuICuICuI(7-MeImPy)](BF4)，本實驗室先前的研究7-Dipy類似，可以抓三個銅金屬，形成三核銅金屬簇離子化合物。這類三核銅簇離子化合物能被氧氣活化形成di(-oxo)的高活性中間物，經由三核銅簇錯化合物的自旋態調控，使其中之一的氧原子被活化至1D狀態，此時會釋放出其中一個架橋氧原子，直接崁入烷類分子的C-H中，可將烷類轉化為醇類。在本篇研究中成功利用[CuICuICuI(7-ImPy)](BF4)和[CuICuICuI(7-MeImPy)](BF4)兩種系統在常溫常壓下將cyclohexane (C-H鍵能為99.3 kcal/mol) 氧化生成cyclohexanol和cyclohexanone，其中催化變得有選擇性，以cyclohexanol為主要產物。
在本研究中使用微波合成取代了傳統的加熱方式，微波可以直接進行內部加熱，使合成含氮配位基的時間可以大幅度的縮短，並且增加純度，減少副產物的產生。
為了證明我們的三核銅簇離子化合物的反應機構是經由單氧直接嵌入(O-atom insertion)而不是經由自由基反應，在三核銅簇離子化合物[CuICuICuI(7-ImPy)](BF4) 和 [CuICuICuI(7-MeImPy)](BF4)的催化反應過程中加入對自由基極為靈敏的化合物5,5-Dimethyl-Pyrroline-N-Oxide (DMPO)，做室溫EPR的測試，發現在整個催化反應的過程中，並沒有偵測到DMPO與自由基反應的EPR訊號，由此證明了此三核銅簇離子化合物的反應機構是經由單氧直接嵌入而非自由基的反應路徑。

關鍵字

微粒體甲烷單氧化酵素 ； 三核銅金屬簇化物 ； 催化

並列摘要

In this study, two new ligands 7-Impy and 7-MeImpy have been synthesized, and they can coordinate with 3 equivalents of CuI ions to form a trinuclear copper complex [CuICuICuI(7-Impy)](BF4) and [CuICuICuI(7-MeImpy)](BF4). These ligands are similar to our previous developed 7-Dipy ligand in the scaffold to trap three CuI ions.
It is known that the hydroxylation of alkane molecules catalyzed by trinuclear copper complexes through the “oxene” insertion mechanism. The active “oxene” with a “1D” spin state will have lower reaction energy barrier when it is tuned by three copper ions.
In this study, these new catalysts, [CuICuICuI(7-ImPy)](BF4) and [CuICuICuI(7-MeImPy)](BF4), are also able to catalyze the oxidation of cyclohexane converting to cyclohexanol and cyclohexanone. Compared to our previous developed 7-Dipy ligand, the catalytic reaction is more favorable for the product of cyclohexanol.
In this study, we replaced traditional heating by microwave for the ligand synthesis. Microwave can enhance internal heating efficiently, which significantly reduce the reaction time, increase the purity, and reduce the byproducts.
In addition, for proving the reaction catalyzed by our trinuclear copper cluster via the O-atom insertion mechanism or radical mechanism, we designed a series of experiments using 5,5-Dimethyl-Pyrroline-N-Oxide (DMPO), which is very sensitive to radical. We added DMPO in catalytic reaction, and measured EPR while in the reaction. We found that there are no radical EPR peaks related to DMPO derivatives, similar to the case of 7-Dipy.

並列關鍵字

Particulate methane monooxygenases ； Trinuclear copper clusters ； Catalysis

參考文獻

1. Olah; George, A. Beyond oil and gas: The methanoleconomy; Wiley-VCH: Weinheim, ALLEMAGNE, 2005, 44.

2. Periana, R. A.; Bhalla, G.; Tenn, W. J.; Young, K. J. H.; Liu, X. Y.; Mironov, O.; Jones, C. J.; Ziatdinov, V. R., Perspectives on some challenges and approaches for developing the next generation of selective, low temperature, oxidation catalysts for alkane hydroxylation based on the CH activation reaction. J. Mol. Catal. A-Chem. 2004, 220 (1), 7-25.

3. Shindell, D. T.; Faluvegi, G.; Koch, D. M.; Schmidt, G. A.; Unger, N.; Bauer, S. E., Improved Attribution of Climate Forcing to Emissions. Science 2009, 326 (5953), 716-718.

5. Lipscomb, J. D. Annu. Rev. Microbiol. 1994, 48, 371.

7. Chan, S. I.; Yu, S. S. F. Accounts Chem. Res. 2008, 41, 969.